Ashes and Oil: Agricultural Production and the Building Industry in North AfricaLynne C. Lancaster (Ohio University)

11 décembre 2009

(Session 3. Outils et matériaux, modérateur : François Villeneuve, Université de Paris I)
In this paper I examine two building materials that illustrate the way in which agricultural practices affected choices in the building industry in North Africa. The first is the use of grass and wheat ash as a pozzolanic additive for creating a hydraulic mortar. Recent experimental studies have shown that ash from grasses and wheat straw, which are high in silica, produce a pozzolanic reaction when mixed with lime mortar. Ash found in the linings of cisterns in North Africa suggests that the builders were using the ash of agricultural byproducts to create hydraulic mortar, as opposed to the more common practice of adding crushed terracotta. The second technique discussed is the use of terracotta vaulting tubes, the proliferation of which in North Africa can be related to imperial agricultural policy during the second century AD that promoted the cultivation of the olive and with it the increased production of terracotta amphoras in which to ship the olive oil; at the same time, the production and export of other terracotta goods increased. I argue that resulting development of the infrastructure for terracotta production during the second century in response to increased olive cultivation made the mass production of the vaulting tubes economically feasible only in the third century, even though the technique was known earlier. The number of tubes that could be fired in an average sized kiln is calculated in order to quantify production levels. These two examples illustrate the ways in which agriculture and building were interrelated both technologically and economically.